This invention relates to an improved atherectomy catheter for severing and removing atheroma, calcific deposits, thrombus and related materials from blood vessel walls, and to components for such catheters. As will be apparent from the following discussion, certain of these components can be used in other types of catheters.
Atherectomy catheters have been proposed for removing material from an atheroma in the vascular system. Gifford U.S. Pat. No. 4,669,469 and Simpson U.S. Pat. No. 4,781,186 disclose two such devices, both of which have a distal end that defines an opening on one side and an inflatable balloon on the other. A rotary cutter is mounted within the distal end to be advanced distally while being rotated so as to cut through material that has been pushed into the opening by the inflated balloon opposite the opening. The device illustrated in the Gifford patent utilizes a guidewire that extends axially through a tube used to rotate and advance the rotary cutter.
Fischell U.S. Pat. No. 4,765,332 discloses an atherectomy catheter that includes a distal tubular blade that cuts as it is pulled proximally. During the actual cutting, the entire blade is exposed around the perimeter of the device.
Another approach is described in Leckrone U.S. Pat. No. 4,685,458, which utilizes a catheter having three lumens. The first lumen receives removed material, the second receives a guidewire, and the third lumen is used to inflate a balloon opposite the material-receiving region of the distal end of the catheter. The disclosed catheter uses laser energy, a heated element or a fixed knife to remove material.
Auth U.S. Pat. No. 4,445,509 discloses a method and apparatus for removing vascular deposits having a rotary cutting tool that defines spirally-shaped cutting flutes shaped to remove relatively more rigid deposits without harming relatively more elastic vascular walls. The disclosed cutter is said to operate preferentially against relatively hard material such as calcific plaque without cutting relatively soft material such as the vessel.
A somewhat similar approach is used in Kensey U.S. Pat. No. 4,747,821 which utilizes a rotary impacting head that is shaped not to harm the visco-elastic vessel wall. However, when the impacting head contacts atherosclerotic tissue, the increased hardness of the tissue is said to render it susceptible to disruption by the impacting head.
Shapiro U.S. Pat. No. 4,819,635 discloses a tubular microsurgery cutting apparatus intended for use in opthamic surgery. This apparatus includes an outer tube that defines a side opening at a distal end through which material to be severed passes. A tubular cutter is mounted within the outer tube and is axially oscillated by a pneumatic system such that the oscillation causes the cutter to move across the entire opening with each stroke. This system appears to contemplate the use of a relatively long stroke, and no means are provided for shifting the center of oscillation of the cutting element along the length of the opening in the outer tube.
It is an object of the present invention to provide an improved atherectomy catheter which is well-suited to the removal of atheroma, calcific deposits and thrombus without damaging the vessel wall, which uses a cutting stroke that is oriented proximally, which captures and removes a large quantity of removed material without requiring the catheter to be removed from the vessel, which utilizes a remarkably flexible housing for the cutter element that facilitates placement of the catheter in small and tortuous vessels, which combines axial oscillation of the cutter element with movement of the center of oscillation along the cutting window to provide improved control and cutting action, and which can be guided to the treatment site by a guidewire which does not occupy volume within the body of the catheter shaft proximally of the cutter element.